Maybe you are not clear on what "zero sum" means? But of course bitcoin is technically negative-sum, because miners don't pay in, but do cash out. And, some fr

Maybe you are not clear on what "zero sum" means? But of course bitcoin is technically negative-sum, because miners don't pay in, but do cash out. And, some fraction of coin is lost and so not cashed out. Whoever can't cash out donated their stake. When it gets where it has been more or less constantly falling for long enough, and everybody wants out, it will fall at an increasing rate, and everybody still holding donated their stake, too.